CAPITAL STOCK AND SHARE-BASED COMPENSATION - Employee Stock Purchase Plan Purchases (Details) - $ / shares |
3 Months Ended | 55 Months Ended | 79 Months Ended | |||||||
---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2018 |
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2018 |
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Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | ||||||||||
Employee Stock Purchase Plan shares issued (shares) | 7,856 | 6,052 | 8,673 | 10,913 | 13,323 | 12,276 | 11,446 | 13,244 | 3,039,200 | 3,122,983 |
Price per Employee Stock Purchase Plan share issued (usd per share) | $ 99.54 | $ 106.22 | $ 72.64 | $ 51.29 | $ 44.80 | $ 47.57 | $ 53.39 | $ 43.43 | $ 14.72 | $ 99.54 |